Spatial modelling of tree seed mast

The spatial modelling of seed masting of trees in Switzerland is based on the observations of MastWeb. A separate model is calculated for each year and each tree species/species.

As explanatory variables for seed production, we use the geographical coordinates (longitude and latitude) and the altitude above sea level. The mast observations are converted into numerical values for the model (0 = mismast, 1 = blast mast, 2 = half mast, 3 = full mast). The model itself is a simple GLM (generalised linear model) with the three explanatory variables as 2nd-degree polygons:

Mast ~ Longitude + Longitude2 + Latitude + Latitude2 + Elevation + Elevation2.

This maximum model is then simplified based on AIC (Akaike information criterion) and the best model is used for spatial projection.

For tree species/years in which less than 20 observations are available, no models are calculated, as a generalisation to Switzerland would be too inaccurate.